Benzoxazines and compositions containing benzoxazine (BZN) are known (see, for example, U.S. Pat. Nos. 5,543,516 and 6,207,786 to Ishida et al.; S. Rimdusit and H. Ishida, “Development of New Class of Electronic Packaging Materials Based on Ternary Systems of Benzoxazine, Epoxy, and Phenolic Resins”, Polymer, 41, 7941-49 (2000); and H. Kimura et al., “New Thermosetting Resin from Bisphenol A-based Benzoxazine and Bisoxazoline”, J. App. Polym. Sci., 72, 1551-58 (1999). Benzoxazine resins are a polymer network forming resin that affords good thermal stability and degradation resistance. Benzoxazine cured networks offer good thermal stability on par with high temperature epoxies, phenolics, and bismaleimides. Benefits of benzoxazine resins include, for example, favorable processing properties, long working time, low cure exotherms, low cure shrinkage, and out-of-autoclave processing.
Phthalonitrile (PN) Resins are a class of network forming resins that supply excellent thermal stability and degradation resistance, yet commercialization of phthalonitrile resin technology and use is hindered by poor processing properties, high cost, and high temperature autoclave cures. Phthalonitrile resins have high melt temperatures due to the rigid structure of many phthalonitrile molecules, which incorporate a large percentage of aromatic structures to maintain the thermal performance of the resin and the networked polymer. The phthalonitrile moiety is also rigid and planar and has a tendency to crystallize. These molecular structure attributes contribute to the high melt temperature of multifunctional PN resins. The high cost of the resin is driven by resin synthesis which utilizes higher cost starting materials similar to anhydride and imide resins and multistep synthesis routes.
Some have experimented with the insertion of a benzoxazine chemical moieties into a phthalonitrile functional molecule followed by gelation of the resin (Brunovska, Z. and H. Ishida, “Thermal study on the copolymers of phthalonitrile and phenylnitrile-functional benzoxazines”, Journal of Applied Polymer Science, 73(14): p. 2937-2949, (1999); and Xu, M., et al., “Design of low temperature self-cured phthalonitrile-based polymers for advanced glass fiber nanonano laminates”, Journal of Materials Science, 48(23): p. 8108-8116, (2013)). A disadvantage of such an approach is the time and cost associated with the chemical synthesis of inserting, for instance, a benzoxazine moiety into a phthalonitrile functional molecule.